ACTA1 and renal fibrosis: Seven days after unilateral ureteral obstruction (UUO) induced renal fibrosis (Figure S5A,B, Supporting Information), we found that ≈ 80% of Col1+ myofibroblasts (Figure4A,E), αSMA+ myofibroblasts (Figure S6A,I, Supporting Information), and POSTN+ myofibroblasts (Figure S6B,J, Supporting Information) in fibrotic kidneys were ZsGreen+ (nonBM‐MSCs lineages), but not tdTomato+ (BM‐MSCs lineages).